Study On The Strength Characteristics Of Fine-grained Tailings Filling Geotextile Tubes

The development of mineral resources in China has boosted China’s economic growth.However,behind the economic growth will also appear some resistance.The development of the mine will produce a large number of fine-grained tailings.Finegrained tailings as a dam material will be low strength,poor stability and other problems.And random storage will affect the surrounding ecological environment.The emergence of the geotextile tube technology provides the right direction for further rational use of fine-grained tailings to solve the problem of dam construction.But there is a lack of research on the mechanical properties of fine-grained tailings filling geotextile tubes,which are directly related to the stability of the dam and need to be studied in depth.In this paper,the fine-grained tailings after the swirl grading of the tailings reservoir of the Shilei tungsten mine in Dayu County,Ganzhou City,Jiangxi Province,were used as the test material.The fine-grained tailings were mixed with water to form a tailings slurry and filled into the geotextile tubes.The fine-grained tailings filling geotextile tubes were tested after consolidating in the chamber.Study the interface shear strength characteristics of fine-grained tailings-filled geotextile tubes at different consolidation times and filling degrees.Mainly including the shear strength of tailings,tailings-geotextile interface,and geotextile tube-geotextile tube interface,and investigate the law of three kinds of interface shear strength.The ultimate compressive strength of the geotextile tubes was obtained by a uniaxial compression test.And the existing theoretical formula was modified to reveal the strengthening mechanism of the geotextile tubes and the damage law under the ultimate load.The finite element method was used to simulate the interface shear process of the fine-grained tailings-filled geotextile tubes.And the stress and deformation law during the shear process of the geotextile tubes was analyzed.In addition,the stability of the geotextile tube method tailings dam under different dam heights and different consolidation times was analyzed.The research results can provide technical support for the subsequent filling of this tungsten mine with geotextile tubes dams and also have reference value for similar fine-grained tailings with the geotextile tube method.The main research contents and conclusions are:(1)The essential characteristics of fine-grained tailings were studied.The basic geotechnical tests were carried out on the fine-grained tailings to obtain their fundamental physical indexes.Meanwhile,the filling tests with different tailing slurry concentrations were carried out on the geotextile tubes.Three filling concentrations were designed: 40%,50% and 60% of tailing slurry,which were combined with the fluidity requirements of the fine-grained tailing slurry in the field construction.The water content after filling and consolidation was compared with the change of consolidation time.It was found that the consolidation rate of tailings slurry with 60%concentration was slightly faster.And the strength of tailings filling geotextile tubes were subsequently studied based on this concentration.(2)Different interfacial shear strength tests of fine-grained tailings-filled geotextile tubes were carried out.Three different filling degrees were designed: low filling degree of 62.5%,medium filling degree of 75%,and high filling degree of 87.5%.Meanwhile,for the convenience of geotextile tubes filling,the tailing sand filling degree was converted into tailing sand filling height in this paper.The geotextile tubes after filling were subjected to tailing sand direct shear test,tailing sand and geotextile interface shear test,filling geotextile tubes and filling geotextile tubes interface shear test under different consolidation time and different filling degrees.By introducing the concept of integrated friction angle and comparing three kinds of interface strength,it was concluded that the overall strength of the tailings filling geotextile tube as a composite body composed of geotextile and tailings is significantly improved.The integrated friction angle of the interface between the geotextile tube and geotextile tube is about 1.07～1.34 times the integrated friction angle of the tailings sand under the influence of different factors.And the shear strength of the interface of the geotextile tubes is greater than the shear strength of the tailings sand is greater than the shear strength of the tailings sand and geotextile interface shear strength.(3)Uniaxial compression strength tests of fine-grained tailings-filled geotextile tubes were carried out.The ultimate compressive strength of the three geotextile tubes in the stacked state was obtained by uniaxial compression tests with different consolidation times and filling degrees.The influence of the filling degree was considered on the basis of the existing theoretical equations for ultimate compressive strength.Corresponding corrections were made,and the error between the ultimate compressive strength test value and the theoretical correction value was less than 4%.At the same time,the damage pattern of the geotextile tubes was analyzed.It was found that the damaged position of the geotextile tubes under uniaxial compression mainly occurs at the bottom surface of the middle geotextile tube.And the lower the filling degree,the more extensive the damage range of the geotextile tubes.(4)Numerical simulation analysis of shear strength at the interface of the geotextile tubes.The ABAQUS finite element software was used to establish the interface shear model of the small-size geotextile tubes.Simulation of this indoor shear test of a fine-grained tailings-filled geotextile tubes.Analyzed the shear process of the tailing sand stress in the geotextile tubes and the deformation law of the geotextile.The interfacial shear stress and displacement curve is compared with the test curve by numerical calculation,and the test curve and the simulation curve are consistent.The interface shear model of large-size geotextile tubes were also established according to the size of the geotextile tubes constructed in the field.And compared with the smallsize geotextile tubes body shear model to compare the difference in stress and deformation of the geotextile tubes under the two sizes.(5)Geo Studio software was used to analyze the overall stability of geotextile tubes dams and conventional tailings dams at different dam heights And it was concluded that the safety factor of the geotextile tube method is significantly greater than that of the traditional tailings dam.It was also concluded that different consolidation times affect the safety factor of the geotextile tube method of dam construction.